In line with increased use of high frequencies for electronic apparatuses, a capacitor, which is one of electronic components, is also ever more demanded to have good impedance characteristic in a high-frequency range. To satisfy this demand, various solid electrolytic capacitors using conductive polymer with high electric conductivity for their solid electrolyte have been examined.
FIG. 5 is a perspective view of capacitor 1 that is a conventional solid electrolytic capacitor. This capacitor 1 is made by laminating multiple capacitor elements 2 in FIG. 6.
A method of manufacturing capacitor element 2 is described next. First, as shown in FIG. 7, dielectric film 4 is formed on both faces of substrate 43 made of aluminum. Next, a conductive film (not illustrated) is formed on dielectric film 4 on the side of one end (end A) of substrate 43. Then, a power supply part of a positive electrode is placed on one face (face 5) on the side of the other end (end B) of substrate 43. Conductive polymer layer 6 is formed on the dielectric film formed on the side of end A by soaking substrate 43 in a monomer solution and applying voltage. Next, negative electrode layer 47 is formed on this conductive polymer layer 6. By removing the power supply part, a face where conductive polymer layer 6 is not formed is exposed on the side of the other end (end B) of substrate 43. This becomes positive electrode 8. Capacitor element 2 is formed by the above steps.
Positive electrode 8 of each capacitor element 2 is led out to positive electrode terminal 9, and negative electrode layer 47 is led out to negative electrode terminal 10 in capacitor 1 shown in FIG. 5.
In conventional capacitor 1, rough surface layers 42 and 45 are formed by vacuum deposition on surfaces of electrode foil (substrate 43) made of aluminum foil on the side of one face 5 and on the side of the other face 11, respectively, in capacitor element 2 with the aim of increasing static capacitance by expanding a surface area per unit volume of substrate 43. Rough surface layer 42 on one face 5 is thicker than rough surface layer 45 on the other face 11.